方式一:採用ServletContext讀取
獲取配置文件的realpath,然後通過文件流讀取出來或者通過方法getReasurceAsStream()。
因爲是用ServletContext讀取文件路徑,所以配置文件可以放入在WEB-INF的classes目錄中,也可以在應用層級及WEB-INF的目錄中。文件存放位置具體在eclipse工程中的表現是:可以放在src下面,也可放在WEB-INF及Web-Root下面等。因爲是讀取出路徑後,用文件流進行讀取的,所以可以讀取任意的配置文件包括xml和properties。缺點:不能在servlet外面應用讀取配置信息。
1.首先創建一個動態的javaweb項目,項目目錄如下:
2.創建一個servlet(FileReader.java)
package com.xia.fileReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.text.MessageFormat;
import java.util.Properties;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class FileReader extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/**
* response.setContentType("text/html;charset=UTF-8");目的是控制瀏覽器用UTF-8進行解碼;
* 這樣就不會出現中文亂碼了
*/
response.setHeader("content-type","text/html;charset=UTF-8");
readSrcDirPropCfgFile(response);//讀取src目錄下的db1.properties配置文件
response.getWriter().println("<hr/>");
readWebRootDirPropCfgFile(response);//讀取WebRoot目錄下的db2.properties配置文件
response.getWriter().println("<hr/>");
readSrcSourcePackPropCfgFile(response);//讀取src目錄下的config目錄中的db3.properties配置文件
response.getWriter().println("<hr/>");
readWEBINFPropCfgFile(response);//讀取WEB-INF目錄下的JDBC目錄中的db4.properties配置文件
}
public void readSrcDirPropCfgFile(HttpServletResponse response) throws IOException {
String path = "/WEB-INF/classes/db1.properties";
InputStream in = this.getServletContext().getResourceAsStream(path);
Properties props = new Properties();
props.load(in);
String driver = props.getProperty("jdbc.driver");
String url = props.getProperty("jdbc.url");
String username = props.getProperty("jdbc.username");
String password = props.getProperty("jdbc.password");
response.getWriter().println("讀取src目錄下的db1.properties配置文件");
response.getWriter().println(MessageFormat.format( "driver={0},url={1},username={2},password={3}",driver,url, username, password));
}
public void readWebRootDirPropCfgFile(HttpServletResponse response) throws IOException{
String path = "/db2.properties";
InputStream in = this.getServletContext().getResourceAsStream(path);
Properties props = new Properties();
props.load(in);
String driver = props.getProperty("jdbc.driver");
String url = props.getProperty("jdbc.url");
String username = props.getProperty("jdbc.username");
String password = props.getProperty("jdbc.password");
response.getWriter().println("讀取WebRoot目錄下的db2.properties配置文件");
response.getWriter().println(MessageFormat.format( "driver={0},url={1},username={2},password={3}",driver,url, username, password));
}
public void readSrcSourcePackPropCfgFile(HttpServletResponse response) throws IOException {
String path = "/WEB-INF/classes/config/db3.properties";
String realPath = this.getServletContext().getRealPath(path);
InputStreamReader reader = new InputStreamReader(new FileInputStream(realPath),"UTF-8");
Properties props = new Properties();
props.load(reader);
String driver = props.getProperty("jdbc.driver");
String url = props.getProperty("jdbc.url");
String username = props.getProperty("jdbc.username");
String password = props.getProperty("jdbc.password");
response.getWriter().println("讀取src目錄下的config目錄中的db3.properties配置文件");
response.getWriter().println(MessageFormat.format( "driver={0},url={1},username={2},password={3}", driver,url, username, password));
}
public void readWEBINFPropCfgFile(HttpServletResponse response) throws IOException {
String path = "/WEB-INF/JDBC/db4.properties";
String realPath = this.getServletContext().getRealPath(path);
System.out.println("realPath:"+realPath);
System.out.println("contextPath:"+this.getServletContext().getContextPath());
InputStreamReader reader = new InputStreamReader(new FileInputStream(realPath),"UTF-8");
Properties props = new Properties();
props.load(reader);
String driver = props.getProperty("jdbc.driver");
String url = props.getProperty("jdbc.url");
String username = props.getProperty("jdbc.username");
String password = props.getProperty("jdbc.password");
response.getWriter().println("讀取WEB-INF目錄下的JDBC目錄中的db4.properties配置文件");
response.getWriter().println(MessageFormat.format( "driver={0},url={1},username={2},password={3}", driver,url, username, password));
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
3.配置servlet(web.xml)
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>javaReaderFile</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>FileReader</servlet-name>
<servlet-class>com.xia.fileReader.FileReader</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FileReader</servlet-name>
<url-pattern>/FileReader</url-pattern>
</servlet-mapping>
</web-app>
4.測試
方式二:採用ResourceBundle類讀取配置信息
優點是:可以以完全限定類名的方式加載資源後,直接的讀取出來,且可以在非Web應用中讀取資源文件。
缺點:只能加載類src下面的資源文件且只能讀取.properties文件。
/**
* 獲取指定配置文件中所有的數據
* @param propertyName
* 調用方式:
* 1.配置文件放在resource源包下,不用加後綴
* PropertiesUtil.getAllMessage("message");
* 2.放在包裏面的
* PropertiesUtil.getAllMessage("com.test.message");
* @return
*/
public static List<String> getAllMessage(String propertyName) {
// 獲得資源包
ResourceBundle rb = ResourceBundle.getBundle(propertyName.trim());
// 通過資源包拿到所有的key
Enumeration<String> allKey = rb.getKeys();
// 遍歷key 得到 value
List<String> valList = new ArrayList<String>();
while (allKey.hasMoreElements()) {
String key = allKey.nextElement();
String value = (String) rb.getString(key);
valList.add(value);
}
return valList;
}
方式三:採用ClassLoader方式進行讀取配置信息
優點是:可以在非Web應用中讀取配置資源信息,可以讀取任意的資源文件信息
缺點:只能加載類src下面的資源文件,不適合裝載大文件,否則會導致jvm內存溢出
package com.xia.fileReader;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Properties;
public class ReadByClassLoader {
public static void main(String[] args) throws IOException {
readPropFileByClassLoad();
}
public static void readPropFileByClassLoad() throws IOException{
//讀取src下面config包內的配置文件db3.properties
InputStream in = ReadByClassLoader.class.getClassLoader()
.getResourceAsStream("config/db3.properties");
BufferedReader br = new BufferedReader(new InputStreamReader(in));
Properties props = new Properties();
props.load(br);
for(Object s: props.keySet()){
System.out.println(s+":"+props.getProperty(s.toString()));
}
}
}
方式四: PropertiesLoaderUtils工具類
/**
* Spring 提供的 PropertiesLoaderUtils 允許您直接通過基於類路徑的文件地址加載屬性資源
* 最大的好處就是:實時加載配置文件,修改後立即生效,不必重啓
*/
private static void springUtil(){
Properties props = new Properties();
while(true){
try {
props=PropertiesLoaderUtils.loadAllProperties("message.properties");
for(Object key:props.keySet()){
System.out.print(key+":");
System.out.println(props.get(key));
}
} catch (IOException e) {
System.out.println(e.getMessage());
}
try {Thread.sleep(5000);} catch (InterruptedException e) {e.printStackTrace();}
}
}
修改Properties
/**
* 傳遞鍵值對的Map,更新properties文件
*
* @param fileName
* 文件名(放在resource源包目錄下),需要後綴
* @param keyValueMap
* 鍵值對Map
*/
public static void updateProperties(String fileName,Map<String, String> keyValueMap) {
//getResource方法使用了utf-8對路徑信息進行了編碼,當路徑中存在中文和空格時,他會對這些字符進行轉換,這樣,
//得到的往往不是我們想要的真實路徑,在此,調用了URLDecoder的decode方法進行解碼,以便得到原始的中文及空格路徑。
String filePath = PropertiesUtil.class.getClassLoader().getResource(fileName).getFile();
Properties props = null;
BufferedWriter bw = null;
try {
filePath = URLDecoder.decode(filePath,"utf-8");
log.debug("updateProperties propertiesPath:" + filePath);
props = PropertiesLoaderUtils.loadProperties(new ClassPathResource(fileName));
log.debug("updateProperties old:"+props);
// 寫入屬性文件
bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(filePath)));
props.clear();// 清空舊的文件
for (String key : keyValueMap.keySet())
props.setProperty(key, keyValueMap.get(key));
log.debug("updateProperties new:"+props);
props.store(bw, "");
} catch (IOException e) {
log.error(e.getMessage());
} finally {
try {
bw.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
案例:Web環境讀取屬性文件
package util;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
import javax.sql.DataSource;
import com.alibaba.druid.pool.DruidDataSourceFactory;
public class DruidUtil {
private static Properties prop = new Properties();
private static DataSource dataSource;
static {
InputStream in = DruidUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
try {
prop.load(in);
dataSource = DruidDataSourceFactory.createDataSource(prop);
} catch (Exception e) {
e.printStackTrace();
}
}
public static DataSource getDataSource() {
return dataSource;
}
public static Connection getConnection() {
Connection conn = null;
try {
conn = dataSource.getConnection();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
}